True, but if you instead of throwing the same exception, threw a new one, you could capture both stacks. But you can never get the stack from the throw point of something created elsewhere.
Precisely.I think there are good reasons why other languages collect the
stack-trace on throw.
Collecting the stack trace at construction would be correct if "throw
new" was literally one statement - if the only time you could throw
was at creation.
That's not the case. We have deferred throws and factory methods for
exceptions, and we have re-throws, so collecting the stack-trace at
construction time doesn't work.
Of course, fixing this would require a BC break, and nobody wants to
even entertain the thought of those :-(
On Thu, May 19, 2016 at 10:30 PM, Ryan Pallas wrote:
you could capture both stacks. But you can never get the stack from the
throw point of something created elsewhere.
catch ( PDOException $e ) {
if ( substr($e->getCode(), 0, 2) === '08' ) {
$this->reconnect();
} else {
throw new PDOException($e->getMessage(), $e->getCode(), $e);
}
}
On Thu, May 19, 2016 at 1:47 PM, Rowan Collins wrote:
action happens.
That's one interpretation, but it doesn't really hold up in all cases.
Consider a catch statement that needs to filter more granularly than the
class name; since you already mentioned PDO, I'll make an example with that:
catch ( PDOException $e ) {
if ( substr($e->getCode(), 0, 2) === '08' ) {
$this->reconnect();
} else {
throw $e;
}
}
Of what value to a subsequent catch statement is the trace of that throw
statement? And why does that "start a new exception flow", but if PDO threw
different sub-classes, you could let one flow through unmodified by
tightening the catch statement?
True, but if you instead of throwing the same exception, threw a new one,On 19/05/2016 19:35, Rasmus Schultz wrote:
Technically, every throw is a new exception "flow" - even if you're >
recycling the Exception instance, it's the throw statement that >
starts the unique stack unwind from the throw site; it's where the >Technically, every throw is a new exception "flow" - even if you're >
recycling the Exception instance, it's the throw statement that >
action happens.
That's one interpretation, but it doesn't really hold up in all cases.
Consider a catch statement that needs to filter more granularly than the
class name; since you already mentioned PDO, I'll make an example with that:
catch ( PDOException $e ) {
if ( substr($e->getCode(), 0, 2) === '08' ) {
$this->reconnect();
} else {
throw $e;
}
}
Of what value to a subsequent catch statement is the trace of that throw
statement? And why does that "start a new exception flow", but if PDO threw
different sub-classes, you could let one flow through unmodified by
tightening the catch statement?
you could capture both stacks. But you can never get the stack from the
throw point of something created elsewhere.
catch ( PDOException $e ) {
if ( substr($e->getCode(), 0, 2) === '08' ) {
$this->reconnect();
} else {
throw new PDOException($e->getMessage(), $e->getCode(), $e);
}
}
Regards,
--
Rowan Collins
[IMSoP]
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Rowan Collins
[IMSoP]
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